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Small but mighty: A mini plasma-powered satellite under construction may launch a new era in space exploration

Small but mighty: A mini plasma-powered satellite under construction may launch a new era in space exploration

The CubeSat’s thruster, whose development is led by PPPL physicist Yevgeny Raitses, holds the promise of increased flexibility for the tiny satellites, more than a thousand of which have been launched by universities, research centers and commercial interests around the world. The proposed propulsion device — powered by plasma — could raise and lower the orbits of CubeSats circling the Earth, a capability not broadly available to small spacecraft today, and would hold the potential for exploration of deep space.

“Essentially, we will be able to use these miniature thrusters for many missions,” Raitses said.

A fleet of CubeSats

One example: A fleet made up of hundreds of such micropowered CubeSats could capture in fine detail the reconnection process in the magnetosphere, the magnetic field that surrounds the Earth, said physicist Masaaki Yamada. Yamada is the principal investigator of the PPPL Magnetic Reconnection Experiment, which studies magnetic reconnection — the separation and explosive snapping together of magnetic field lines in plasma that triggers auroras, solar flares and geomagnetic storms that can disrupt cell phone service and power grids on Earth.

Key advantage

The miniaturized engine scales down a cylindrical thruster with a high volume-to-surface geometry developed at the PPPL Hall Thruster Experiment, which Raitses leads and launched with PPPL physicist Nat Fisch in 1999. The experiment investigates the use of plasma — the state of matter composed of free-floating electrons and atomic nuclei, or ions — for space propulsion.

A key advantage of the miniaturized cylindrical Hall thruster will be its ability to produce a higher density of rocket thrust than existing plasma thrusters used for most CubeSats now orbiting Earth. The miniaturized thruster can achieve both increased density and a high specific impulse — the technical term for how efficiently a rocket burns fuel — that will be many times greater than that produced by chemical rockets and cold-gas thrusters typically used on small satellites.

High specific-impulse thrusters use much less fuel and can lengthen satellite missions, making them more cost-effective. Equally important is the fact that a high specific impulse can produce a large enough increase in a satellite’s momentum to enable the spacecraft to change orbits — a feature not available on currently orbiting CubeSats. Finally, high thrust density will enable satellites to accomplish complex fuel-optimized orbits in a reasonable time.

These capabilities provide many benefits. For example, a CubeSat might descend to lower orbit to track hurricanes or monitor shoreline changes and return to a higher orbit where the drag force on a satellite is weaker, requiring less fuel for propulsion.

The foot-long CubeSat, which Princeton has dubbed a “TigerSat,” consists of three 4-inch aluminum cubes stacked vertically together. Sensors, batteries, radio equipment and other instruments will fill the CubeSat, with a miniaturized thruster roughly equal in diameter to two U.S. quarters housed at either end. A thruster will fire to change orbits when the satellite passes the Earth’s equator.

Mechanical and aerospace engineering students

Building the CubeSat are some 10 Princeton graduate and undergraduate students in the Department of Mechanical and Aerospace Engineering, with Daniel Marlow, the Evans Crawford 1911 Professor of Physics, serving as faculty advisor. Undergraduates include Andrew Redd (Class of 2020), who leads design and construction of the CubeSat, and Seth Freeman (Class of 2022), who is working full-time on the project over the summer. Working on thruster development is Jacob Simmonds, a third-year graduate engineering student, whose thesis advisors are Raitses and Yamada. “This project began as a prototype of Yamada’s CubeSat and has evolved into its own project as a testbed for the plasma thruster,” Simmonds said.

Also under construction at PPPL is a test facility designed to simulate key aspects of the CubeSat’s operation. Undergraduates working on their own time are building the satellite and this facility. “To the extent that students and their advisors have identified well-defined questions associated with the TigerSat project, they can get independent work credit,” Marlow said.  “Also, some problem sets in the introductory physics course for undergraduates that I teach have questions related to the TigerSat flight plan.”

Simmonds, while working on the thruster, is drafting a proposal for NASA’s Cubic Satellite Launch Initiative that is due in November. Projects selected by the Initiative, which promotes public-private technology partnerships and low-cost technology development, have launch costs covered on commercial and NASA vehicles. Plans call for a TigerSat launch in the fall of 2021.

Value of collaboration

For Raitses, this project demonstrates the value of Princeton engineering students collaborating with PPPL and of University faculty cooperating with the Laboratory. “This is something that is mutually beneficial,” he said, “and something that we want to encourage.”

Materials provided by Princeton University

ExoMars prototype rover

Radio science instrument for ExoMars 2020 mission ready for the Red Planet

ESA’s Lander Radioscience experiment (LaRa) for ExoMars Mission 2020 has completed its testing in conditions similar to Mars and will be carried to Russia for its acceptance review, followed by integration onto the Kazachok Surface Platform.

At about 8 x 8 x 20 cm and a trio of antennas, LaRa is a high-operating transponder maintaining an extremely stable direct radio-frequency link between Earth and Mars for a full Martian year. LaRa has been planned by the Royal Observatory of Belgium, developed through ESA’s PRODEX programme and funded by the Belgian Space Policy Office.

The latest testing of LaRa was done in ESA’s Mechanical Systems Laboratory (MSL) at the Agency’s ESTEC technical heart in Noordwijk, the Netherlands. It is able to perform space simulation test, serving spacecrafts, mini-satellites, subsystems.

After vibration testing on an MSL shaker for simulating harsh launch conditions, atmosphere re-entry, landing on Mars, LaRa was placed inside a thermal vacuum chamber for functional testing in hot and cold conditions. At first, it was kept in high vacuum to outgas fumes which could pose problems in space. Then it faced simulated Martian conditions, with 6 millibars of carbon dioxide and varying temperature to test its performance. The electronic box of LaRa will be kept warm by the heater of ExoMars lander.

Developed in collaboration between ESA and Université Catholique de Louvain, the unique antenna will be installed outside the thermally controlled conditions to withstand extreme temperature as cold as -90°C and as hot as 10°C. Engineers advanced to remove sensors and cables fitted for testing after opening the thermal chamber before placing the instrument along with the antennas into sterile bags to avoid microbial infection.

Lieven Thomassen of LaRa prime contractor Antwerp Space said that the interior is made of four layers of circuit board which has been cleaned fully. It is completely sealed, with only 2mm diameter hole to avoid excess pressure in space.

LaRa is one of the two ESA instruments on the ExoMars Surface Platform. The first role of the platform is to make sure that itself and the Rosalind Franklin ExoMars rover, also made by ESA safely lands on the Oxia Planum lowlands in Mars. Then Kazachok will be running 13 experiment packages aboard. LaRa will be receiving X-band radio signal from Earth which will be relayed back again. By measuring the small Doppler shifts in this two-way signal, scientists will identify small periodic shifts in the position of Surface Platform as time passes.

Véronique Dehant of the Royal Observatory Belgium, the instrument’s principal investigator said that this will disclose information of planet’s internal structure, accurate calculation of its rotation and orientation and variation in angular momentum due to mass redistribution such as seasonal transfer of mass in carbon dioxide when a portion of the atmosphere freezes. The main challenge is to maintain the highly stable direct radio link in the planned operating schedule of LaRa, that is two sessions of an hour each per week, especially when Mars is at a maximum distance of 401 million km from Earth.

ESA microwave engineer Václav Valenta, manager of the LaRa project said that they will be using huge 70m antennas of Deep Space Network of NASA for transmitting X-band radio signal towards Mars and to pick up a delayed replica with as low as 5W of radio power generated by LaRa.

On Mars, LaRa will need enough sensitivity to detect very low radio signals. When Earth and Mars approach closer, the Estrack ground stations of Europe will close the link with LaRa. This was successfully tested in the radio frequency compatibility tests in ESOC mission control center in Darmstadt, Germany.

The atmosphere of Mars is a complicating factor. It enables convection for carrying away the waste heat. Though thinner than the atmosphere of Earth, radiofrequency operation leaves a risk of corona effects. Václav said that LaRa was formerly subjected to ESA’s High Power Radio Frequency Laboratory to remove corona risk which is ionization of local gases leading to adverse lightning-like discharge.

It also was tested inside the Maxwell chamber of ESTEC for electromagnetic compatibility to check that all the elements work properly. For verifying the robustness of LaRa against mechanical shocks due to the carrier module separation, a shock model was developed and tested at ESTEC Test Centre. After testing was completed, it was moved to ESA’s Metrology Laboratory for accurate measurements of its surface flatness for perfect fit and thermal contact with its lander interface to maintain a proper operational temperature.

After that, it will be moved to the Space Research Institute of the Russian Academy of Sciences, IKI for final approval testing followed by full assembly-level testing at Cannes in France. Václav said that the LaRa team worked very hard as actual developments for the flight model started a year late. ExoMars 2020 will be launched by the Russian Proton launcher from Baikonur, Kazakhstan on July 2020.

Starlink Mission

SpaceX loses contact with 3 of its starlink internet satellites

Recently, the well-renowned company SpaceX had launched the first batch of its much awaited “Starlink” program satellites. The commencement witnessed 60 spacecraft which were launched in the orbit which is very close to the earth.

In the recent report provided by SpaceX revealed that they are no more in touch with three of the 60 internet satellites.

Apart from these three satellites, SpaceX has said that the remaining 57 spacecrafts are working in an apropos manner. 45 of these 57 Starlink satellites have reached their desired orbit which is 342 miles from earth. Five satellites are still in the process to raise their orbits and there are another 5 satellites which are under system checks for future launching.

For the last 2 spacecrafts, SpaceX plans to test their deorbiting feature and for that, they will be crashing them straight into earth’s atmosphere though they do not have any problems. The remaining three failed satellites will crash into earth within a year due to their positioning in a lower orbit.

This failure hasn’t perturbed SpaceX and its higher authorities as they claim that the technology used is relatively new and thus prone to error. This kind of reaction from SpaceX has made people think about how they have been permitted for such a project. To support the launching of this project, Elon Musk-led company says that they have taken permission from the Federal Communications Commission. This permission grants them to place nearly 12000 small spacecrafts in the upcoming 8 years.

The main agenda behind this project is to provide ubiquitous internet with high bandwidth. For the same purpose, this Starlink constellation will be used for streaming videos and will also enable to play high bandwidth games aiding them to understand the operability and latency.

On the other hand, the failure of those three satellites has caused contemplation amongst the space scholars who think that the debris will enhance the chances of the collision leading to catastrophic results. This has come at a time where NASA’s research says that almost 99% of satellites should be removed within half a decade for the proper functioning of necessary space projects.

To bolster their point, Elon Musk has assured that his company is in touch with the US Air Force which helps them in locating their spacecrafts and avoid any kind of collisions. Along with this, Musk has also spoken about their initiative to contact different astronomy groups for taking their guidance which will provide a path to make necessary amendments in their systems.

Falcon Heavy Side Boosters landing

SpaceX Falcon Heavy launches its first commercial mission and achieves triple booster landing

The Falcon Heavy rocket of SpaceX which is the most powerful flying vehicle today successfully launched its first commercial mission. It also managed to land all the three rocket boosters successfully. This is after a year when its testing mission landed a red Tesla in space.

This mega rocket took off from the NASA Kennedy Space Center in Florida on Thursday from the same launching pad 39A which once hosted the historic NASA’s Apollo missions. The rocket launched the communications satellite, ArabSat-6A, which is intended to provide internet and related communication services to the people from the Middle East, Africa and also some parts of Europe.

Falcon Heavy had to wait for a day due to unfavorable weather conditions at the launch site, but the second flight took off without any problems at the initial stages of the 2 hour launching attempt. A Falcon Heavy rocket comprises of three first stages of Falcon 9 which combines to make the megarocket of 27 engines. The launch featured Block 5 version of its rockets which is an upgrade from the demo launch of Falcon Heavy.

The special appeal of Falcon Heavy is due to its reusable hardware. The rocket boosters are landed back on Earth so that they are refurbished and be fit to use again. This approach can reduce the cost of spaceflight to a great extent. This Block 5 Falcon 9 can fly as many as 9-10 times without any refurbishment between flights which is a massive upgrade from its earlier 2-3 times. This was made possible due to the design changes which were brought by the engineers which included improvement in the engines, a durable interstage( the connecting piece between the two stages of rocket), an enhanced thermal protection method.

In this attempt, two out of three side-boosters landed safely on the grounded pads in Florida while the central third one landed on SpaceX’s platform controlled remotely on the Atlantic Ocean. This is a significant achievement on the side of rocket launch and satellite transmission as the Falcon heavy boasts of twice more power but one third the price of Delta IV Heavy of the United Launch Alliance, which is a joint venture between the Boeing and Lockheed Martin for government contracts which need launch vehicles for heavy lift operations.

Falcon Heavy has been already awarded a $130 million contract for launching satellites of US Air Force, just four months after its initial testing in last year February. The rocket will be primarily used for military missions for the United States and deploying commercial telecommunication satellites.